Recent views of learning and memory in aging have suggested that many of the learning and memorial difficulties encountered by elderly persons can be traced to the decline in central processing capacity that seems to occur with normal aging. These "reduced-capacity" hypotheses suggest that mnemonic processing might be more demanding for the older person, so that he/she often has to devote more cognitive effort, or work harder, in carrying out the various kinds of mnemonic operations that underly optimal learning and memory performance. The aim of this project is to evaluate these reduced-capacity hypotheses by using a secondary task methodology to directly measure age differences in the capacity demands of mnemonic processing. In the experiments proposed in this project, elderly and young subjects will perform several kinds of secondary tasks as they are carrying out "deep" levels of processing, verbal mediation, imagery processing, and organization. Subjects' performance on both discrete and continuous secondary tasks will be used to test the general hypothesis that memory processing is more demanding in aging, with specific experiments designed to: a) confirm age differences in the demands of these various kinds of processes; b) determine whether the elderly are more "fatigued" by the requirement of carrying out such processing; and c) determine whether age-related difficulties might reflect decline in modality-specific processing capacity. In related experiments, the secondary task methodology will be used to determine whether the older subject's difficulties can be reduced by practice, or through pre-experimental knowledge. Finally, additional experiments will require subjects to perform a secondary task during retrieval, in order to analyze the relationship between age differences in organization and corresponding differences in the demands of free recall. This project is intended to identify one factor that might underly many of the specific kinds of processing deficits that characterize learning and memory in aging, and it is also intended to identify conditions that might be expected to improve the faulty processing of older persons.